The invention relates to golf equipment including polyurea compositions. In particular, the present invention is directed to golf equipment including compositions formed from a polyurea prepolymer of polyether amine and isocyanate crosslinked with a curing agent, and methods for making same. Preferably, the components of the composition are saturated, i.e., substantially free of unsaturated carbon-carbon bonds or aromatic groups, to produce a light stable composition.
Golf equipment, i.e., clubs and balls, are formed from a variety of compositions. For example, golf ball covers are formed from a variety of materials, including balata and ionomer resins. Balata is a natural or synthetic trans-polyisoprene rubber. Balata covered balls are favored by more highly skilled golfers because the softness of the cover allows the player to achieve spin rates sufficient to more precisely control ball direction and distance, particularly on shorter shots.
However, balata covered balls are easily damaged, and thus lack the durability required by the average golfer. Accordingly, alternative cover compositions have been developed in an attempt to provide balls with spin rates and a feel approaching those of balata covered balls, while also providing a golf ball with a higher durability and overall distance.
Ionomer resins have, to a large extent, replaced balata as a cover material. Chemically, ionomer resins are a copolymer of an olefin and an xcex1, xcex2-ethylenically-unsaturated carboxylic acid having 10 to 90 percent of the carboxylic acid groups neutralized by a metal ion, as disclosed in U.S. Pat. No. 3,264,272. Commercially available ionomer resins include, for example, copolymers of ethylene and methacrylic or acrylic acid, neutralized with metal salts. Examples of commercially available ionomer resins include, but are not limited to, SURLYN(copyright) from DuPont de Nemours and Company, and ESCOR(copyright) and IOTEK(copyright) from Exxon Corporation. These ionomer resins are distinguished by the type of metal ion, the amount of acid, and the degree of neutralization.
U.S. Pat. Nos. 3,454,280, 3,819,768, 4,323,247, 4,526,375, 4,884,814, and 4,911,451 all relate to the use of SURLYN(copyright)-type compositions in golf ball covers. However, while SURLYN(copyright) covered golf balls, as described in the preceding patent, possess virtually cut-proof covers, the spin and feel are inferior compared to balata covered balls.
Polyurethanes have also been recognized as useful materials for golf ball covers since about 1960. U.S. Pat. No. 3,147,324 is directed to a method of making a golf ball having a polyurethane cover. The resulting golf balls are durable, while at the same time maintaining the xe2x80x9cfeelxe2x80x9d of a balata ball.
Various companies have investigated the usefulness of polyurethane as a golf ball cover material. U.S. Pat. No. 4,123,061 teaches a golf ball made from a polyurethane prepolymer formed of polyether with diisocyanate that is cured with either a polyol or an amine-type curing agent. U.S. Pat. No. 5,334,673 discloses the use of two categories of polyurethane available on the market, i.e., thermoset and thermoplastic polyurethanes, for forming golf ball covers and, in particular, thermoset polyurethane covered golf balls made from a composition of polyurethane prepolymer and a slow-reacting amine curing agent, and/or a difunctional glycol.
Unlike SURLYN(copyright) covered golf balls, polyurethane golf ball covers can be formulated to possess the soft xe2x80x9cfeelxe2x80x9d of balata covered golf balls. However, golf ball covers made from polyurethane have not, to date, fully matched SURLYN(copyright) golf balls with respect to resilience or the rebound of the golf ball cover, which is a function of the initial velocity of a golf ball after impact with a golf club.
Furthermore, because the polyurethanes used to make the covers of such golf balls generally contain an aromatic component, e.g., aromatic diisocyanate, polyol, or polyamine, they are susceptible to discoloration upon exposure to light, particularly ultraviolet (UV) light. To slow down the discoloration, light and UV stabilizers, e.g., Tinuvin 770, 765, and 328, are added to these aromatic polymeric materials. However, to further ensure that the covers formed from aromatic polyurethanes do not appear discolored, the covers are painted with white paint and then covered with a clear coat to maintain the white color of the golf ball. The application of a uniform white pigmented coat to the dimpled surface of the golf ball is a difficult process that adds time and costs to the manufacture of a golf ball.
Polyureas have also been proposed as cover materials for golf balls. For instance, U.S. Pat. No. 5,484,870 discloses a polyurea composition comprising the reaction product of an organic diisocyanate and an organic amine, each having at least two functional groups. Once these two ingredients are combined, the polyurea is formed, and thus the ability to vary the physical properties of the composition is limited. Like polyurethanes, polyureas are not completely comparable to SURLYN(copyright) golf balls with respect to resilience or the rebound or damping behavior of the golf ball cover.
Therefore, there remains a continuing need for golf equipment having soft components that provide improved resilience, increased cut, scratch and abrasion resistance, and enhanced adherence without adversely affecting overall performance characteristics of the golf balls. In addition, it would be advantageous to provide a composition that combines the cut and scratch resistance with improved resistance to discoloration that are suitable for forming golf ball components and other golf-related equipment.
The invention is directed to golf equipment having at least a portion formed of a polyurea composition. In one embodiment, the present invention is directed to one-piece golf balls including polyurea. In another embodiment, the compositions of the invention are used in two-piece and multi-component, e.g., three-piece, four-piece, etc. golf balls including at least one cover layer and a core, wherein at least one cover layer includes at least one polyurea, as well as multi-component golf balls including cores and/or covers having two or more layers, wherein at least one such layer(s) is formed of at least one polyurea.
More particularly, the present invention is directed, in a first embodiment, towards a golf ball including at least a cover and at least one core layer wherein the cover is formed from a composition including at least one polyurea composition formed from a polyurea prepolymer of diisocyanate and polyether amine cured with a curing agent.
The present invention is further directed in a second embodiment towards a golf ball including a cover, a core and at least one intermediate layer interposed between the cover and an outermost core layer, wherein the intermediate layer is formed from a composition including a polyurea prepolymer of diisocyanate and polyether amine cured with a curing agent
The present invention is yet further directed in a third embodiment towards a golf ball including a cover, a core, and at least one intermediate layer interposed between the cover and the core, wherein the outermost cover layer and at least one intermediate layer are both formed from a polyurea composition including a polyurea prepolymer of diisocyanate and polyether amine cured with a curing agent.
In the golf ball cover embodiment of the present invention, the polyurea preferably includes from about 1 to about 100 weight percent of the cover, with the remainder of the cover, if any, including one or more compatible, resilient polymers such as would be known to one of ordinary skill in the art.
The invention is further directed to a golf ball including at least one light stable cover layer formed from a composition including at least one polyurea formed from a polyurea prepolymer and a curing agent. In one embodiment, the polyurea prepolymer includes at least one diisocyanate and at least one polyether amine.
In this aspect of the invention the diisocyanate is saturated, and selected from the group consisting of ethylene diisocyanate; propylene-1,2-diisocyanate; tetramethylene diisocyanate; tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate; octamethylene diisocyanate; decamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate; dicyclohexylmethane diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate; methylcyclohexylene diisocyanate; 2,4-methylcyclohexane diisocyanate; 2,6-methylcyclohexane diisocyanate; 4,4xe2x80x2-dicyclohexyl diisocyanate; 2,4xe2x80x2-dicyclohexyl diisocyanate; 1,3,5-cyclohexane triisocyanate; isocyanatomethylcyclohexane isocyanate; 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; isocyanatoethylcyclohexane isocyanate; bis(isocyanatomethyl)-cyclohexane diisocyanate; 4,4xe2x80x2-bis(isocyanatomethyl)dicyclohexane; 2,4xe2x80x2-bis(isocyanatomethyl)dicyclohexane; isophoronediisocyanate; triisocyanate of HDI; triisocyanate of 2,2,4-trimethyl-1,6-hexane diisocyanate; 4,4xe2x80x2-dicyclohexylmethane diisocyanate; 2,4-hexahydrotoluene diisocyanate; 2,6-hexahydrotoluene diisocyanate; and mixtures thereof. The saturated diisocyanate is preferably selected from the group consisting of isophoronediisocyanate, 4,4xe2x80x2-dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate, or a combination thereof.
In another embodiment, the diisocyanate is an aromatic aliphatic isocyanate selected from the group consisting of meta-tetramethylxylene diisocyanate; para-tetramethylxylene diisocyanate; trimerized isocyanurate of polyisocyanate; dimerized uredione of polyisocyanate; modified polyisocyanate; and mixtures thereof.
The polyether amine may be selected from the group consisting of polytetramethylene ether diamines, polyoxypropylene diamines, poly(ethylene oxide capped oxypropylene)ether diamines, triethyleneglycoldiamines, propylene oxide-based triamines, trimethylolpropane-based triamines, glycerin-based triamines, and mixtures thereof. In one embodiment, the polyether amine has a molecular weight of about 1000 to about 3000.
The curing agent may be selected from the group consisting of hydroxy-terminated curing agents, amine-terminated curing agents, and mixtures thereof, and preferably has a molecular weight from about 250 to about 3900.
In one embodiment, the hydroxy-terminated curing agents are selected from the group consisting of ethylene glycol; diethylene glycol; polyethylene glycol; propylene glycol; 2-methyl-1,3-propanediol; 2-methyl-1,4-butanediol; dipropylene glycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol; 1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol; trimethylolpropane; cyclohexyldimethylol; triisopropanolamine; tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycol di-(aminopropyl)ether; 1,5-pentanediol; 1,6-hexanediol; 1,3-bis-(2-hydroxyethoxy)cyclohexane; 1,4-cyclohexyldimethylol; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]cyclohexane; 1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane; trimethylolpropane; polytetramethylene ether glycol, preferably having a molecular weight from about 250 to about 3900; and mixtures thereof.
The amine-terminated curing agents may be selected from the group consisting of ethylene diamine; hexamethylene diamine; 1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine; 4,4xe2x80x2-bis-(sec-butylamino)-dicyclohexylmethane; 1,4-bis-(sec-butylamino)-cyclohexane; 1,2-bis-(sec-butylamino)-cyclohexane; derivatives of 4,4xe2x80x2-bis-(sec-butylamino)-dicyclohexylmethane; 4,4xe2x80x2-dicyclohexylmethane diamine; 1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine); diethylene glycol di-(aminopropyl)ether; 2-methylpentamethylene-diamine; diaminocyclohexane; diethylene triamine; triethylene tetramine; tetraethylene pentamine; propylene diamine; 1,3-diaminopropane; dimethylamino propylamine; diethylamino propylamine; imido-bis-propylamine; monoethanolamine, diethanolamine; triethanolamine; monoisopropanolamine, diisopropanolamine; isophoronediamine; and mixtures thereof.
In one embodiment, the composition further includes a catalyst selected from the group consisting of a bismuth catalyst, zinc octoate, di-butyltin dilaurate, di-butyltin diacetate, tin (II) chloride, tin (IV) chloride, di-butyltin dimethoxide, dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctyl mercaptoacetate, triethylenediamine, triethylamine, tributylamine, oleic acid, acetic acid; delayed catalysts, and mixtures thereof. The catalyst may be present from about 0.005 percent to about 1 percent by weight of the composition.
In another embodiment, the cover layer has a difference in yellowness index of about 12 or less after 5 days of ultraviolet light exposure. In yet another embodiment, the cover layer has a difference in b chroma dimension of about 6 or less after 5 days of ultraviolet light exposure.
In this aspect of the invention, the cover layer may be formed from casting, injection molding, or reaction injection molding.
The present invention is also directed to a golf ball including a core, a layer disposed about the core forming a center, and a cover cast onto the center, wherein the cover comprises a light stable polyurea material comprising at least a diisocyanate, at least a polyether amine, and at least one of a hydroxy-terminated curing agent, a amine-terminated curing agent, or a mixture thereof.
In one embodiment, the layer comprises ionomers, polyamides, highly neutralized polymers, polyesters, polycarbonates, polyimides, polyolefins, acid copolymers, polyurethanes, vinyl resins, acrylic resins, polyphenylene oxide resins, metallocene catalyzed polymers, and mixtures thereof. In another embodiment, the layer is a moisture barrier layer.
In yet another embodiment, the cover has a thickness of about 0.02 inches to about 0.035 inches. In addition, the layer preferably has a first Shore D hardness and the cover has a second Shore D hardness, wherein the ratio of second Shore D hardness to the first Shore D hardness is about 0.7 or less.
The core may include polybutadiene and may have a diameter of about 1.55 or greater. In one embodiment, the core includes a cis-to-trans catalyst, a resilient polymer component, and a free radical source. The cis-to-trans catalyst may include an organosulfur component, a Group VIA component, an inorganic sulfide component, an aromatic organic compound, or mixtures thereof.
In one embodiment, at least one of the core, the layer, the cover, or combinations thereof comprise a density-adjusting filler.
The present invention is also directed to a method of forming a golf ball including the steps of providing a golf ball center, mixing a polyurea prepolymer and at least one curing agent to form a castable reactive polyurea liquid material, filling a first set of mold halves with a first amount of the material, lowering the center into the first set of mold halves after a first predetermined time, wherein the center is held by vacuum for a second predetermined time, and wherein the second predetermined time is sufficient for complete exothermic reaction of the first amount of material, releasing the center from the vacuum providing a partially covered center, filling a second set of mold halves with a second amount of the material, wherein the first and second amounts are substantially similar, and wherein an exothermic reaction of the second amount commences, and mating the second set of mold halves with the partially covered center, wherein the exothermic reaction of the second amount concludes.
In one embodiment, the first predetermined time is about 40 seconds to about 100 seconds. In another embodiment, the second predetermined time is about 4 seconds to about 12 seconds.
The polyurea prepolymer may include at least one diisocyanate and at least one polyether amine. In one embodiment, the step of mixing a polyurea prepolymer and at least one curing agent further includes mixing at least one triol or at least one tetraol, or mixtures thereof. In another embodiment, the step of mixing a polyurea prepolymer and at least one curing agent further includes mixing at least one catalyst, at least one light stabilizer, at least one defoaming agent, at least one acid functionalized moiety, or combinations thereof.
In yet another embodiment, the step of providing a golf ball center includes the steps of providing a golf ball core and forming a layer disposed about the golf ball core. In still another embodiment, the golf ball core includes a polybutadiene reaction product, wherein the core has a diameter of about 1.55 or greater, and wherein the layer has a thickness of about 0.02 inches to about 0.035 inches.